Magnetostrictive alternator

ABSTRACT

A magnetostrictive alternator configured to convert pressure waves into electrical energy is provided. It should be appreciated that the magnetostrictive alternator may be combined in some embodiments with a Stirling engine to produce electrical power. The Stirling engine creates the oscillating pressure wave and the magnetostrictive alternator converts the pressure wave into electricity. In some embodiments, the magnetostrictive alternator may include aerogel material and magnetostrictive material. The aerogel material may be configured to convert a higher amplitude pressure wave into a lower amplitude pressure wave. The magnetostrictive material may be configured to generate an oscillating magnetic field when the magnetostrictive material is compressed by the lower amplitude pressure wave.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional of, and claims priority to, U.S.Provisional Patent Application Ser. No. 61/677,116, filed Jul. 30, 2012,the subject matter of which is hereby incorporated by reference in itsentirety.

ORIGIN OF THE INVENTION

The invention described herein was made in the performance of work undera NASA contract and is subject to the provisions of Section 305 of theNational Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat.435; 42 U.S.C. 2457).

FIELD

The present invention relates to alternators and, more particularly, toa magnetostrictive alternator configured to convert pressure waves intoelectrical energy.

BACKGROUND

Stirling engines use alternators, such as moving linear magnetalternators, to convert mechanical motion into electrical energy. Forinstance, conventional alternators use a piston that moves a magnetand/or coil, and the change in magnetic field induces a current in thecoil to deliver electric power to the load. However, with the use ofmoving pistons, the frequency, efficiency, and maximum power output ofthe energy produced by such alternators is limited.

Accordingly, an improved alternator may be beneficial.

SUMMARY

Certain embodiments of the present invention may provide solutions tothe problems and needs in the art that have not yet been fullyidentified, appreciated, or solved by current alternators. For instance,some embodiments of the present invention replace an oscillating linearalternator with an impedance and resonance matched magnetostrictivebased transducer.

In one embodiment, an apparatus is provided. The apparatus includesaerogel material and magnetostrictive material. The aerogel material isconfigured to convert a higher amplitude pressure wave into a loweramplitude pressure wave. The magnetostrictive material is configured togenerate an oscillating magnetic field when the magnetostrictivematerial is compressed by the lower amplitude pressure wave.

In another embodiment, an apparatus is provided. The apparatus includesan absorbing material and a compressing material. The absorbing materialis configured to convert a higher amplitude pressure wave into a loweramplitude pressure wave. The compressing material is configured togenerate an oscillating magnetic field when the compressing material iscompressed by the lower amplitude pressure wave.

In yet another embodiment, an apparatus is provided. The apparatusincludes an absorbing material and a piezoelectric material. Theabsorbing material is configured to convert a higher amplitude pressurewave into a lower amplitude pressure wave. The piezoelectric material isconfigured to generate an oscillating electric field when the loweramplitude pressure wave is applied to the piezoelectric material.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of certain embodiments of the inventionwill be readily understood, a more particular description of theinvention briefly described above will be rendered by reference tospecific embodiments that are illustrated in the appended drawings.While it should be understood that these drawings depict only typicalembodiments of the invention and are not therefore to be considered tobe limiting of its scope, the invention will be described and explainedwith additional specificity and detail through the use of theaccompanying drawings, in which:

FIG. 1A illustrates a magnetostrictive alternator, according to anembodiment of the present invention.

FIG. 1B illustrates a magnetostrictive resonator, according to anembodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Some embodiments of the present invention pertain to a Stirlingmagnetostrictive alternator having stacked magnetostrictive materialunder a biased magnetic and stress induced compression with continuousgradient impedance matching material. Alternating compression andexpansion of the magnetostrictive material may be configured to createan alternating magnetic field to induce an electric current in a coilthat is wrapped around the magnetostrictive material. This allowsproduction of electrical power from the acoustic pressure wave.

FIG. 1A illustrates a magnetostrictive alternator 100, according to anembodiment of the present invention. Magnetostrictive alternator(hereinafter “alternator”) 100 may be operated as an electrical powersource that is connected to, and provides power to, a Stirling engine.As shown in FIG. 1A, alternator 100 includes a stack of magnetostrictivematerial 105, such as Terfenol-D™, Nickel, Nitinol or Galfenol, or anymaterial that would be appreciated by a person of ordinary skill in theart. In other embodiments, piezoelectric material, or any type ofmaterial that can be compressed by a pressure force, may be useddepending on the configuration of alternator 100. In certainembodiments, the stack of magnetostrictive material 105 is wrapped incoils. The coils may be composed of copper, aluminum, or anyelectrically conductive material that can be enveloped by an insulatingmaterial and wound into a coil. It should be appreciated that ifpiezoelectric material is used, then a coil may not be wrapped aroundthe piezoelectric material.

It should be appreciated that in some embodiments, a pre-stress (orcompression) is applied to magnetostrictive material 105. This allowsfor an increase in power output. To achieve an increase in power output,pre-stress permanent magnets 110 and pre-stress bolts 115 are used tocompress, or increase stress on, the stack of magnetostrictive material105 to an ideal location in terms of the linear range ofmagnetostrictive material 105 for producing an increase in electricalpower output.

Pre-stress permanent magnets 110 in this embodiment are configured toprovide a magnetic field causing magnetostrictive material 105 to remainin a compressed state. In some embodiments, secondary pre-stress coilsmay be used for this purpose, but this may require a separate powersource to produce the magnetic field. The pre-stress effect maximizesthe efficiency of magnetostrictive material 105. It should be noted thatwithout pre-stress permanent magnets 110, the power output may bereduced.

Stated differently, magnetostrictive material 105 is compressed to allowmagnetostrictive material 105 to include some force. In other words, apredefined amount of pre-stress is applied to magnetostrictive material105. Thus, when a fairly high amplitude pressure wave 145, which isproduced by a Stirling engine (or another acoustic source), reachesalternator 100, pressure wave 145 causes further compression ofmagnetostrictive material 105 to generate an increase in electricalpower output. In certain embodiments, pressure wave 105 may be anoscillating pressure wave. Because pressure wave 105 may move helium orother atoms approximately 5 mm in either direction and to preventpressure wave 105 from reflecting off of magnetostrictive material 105,a varying density aerogel 125 is utilized for impedance matching withmagnetostrictive material 105. It should be noted that any type ofabsorbing material, which can impedance match, may be used. This allowsenergy from pressure wave 145 to be absorbed into magnetostrictivematerial 105, creating a greater output of electrical power. It shouldbe appreciated that other impedance matching materials, such as steelrods, may be used instead of aerogel. However, this depends on theStirling engine operating parameters.

Certain embodiments may include a protective diaphragm 140 to help keepaerogel 125 from breaking up. An impedance layer support 130 surroundsaerogel 125 to hold aerogel 125 in place.

As mentioned above, aerogel 125 may be configured to absorb pressurewave 145 to avoid reflection, and change a high amplitude of pressurewave 145 to a lower (or smaller) amplitude pressure wave (not shown)without losing the energy in the pressure wave, allowing the energy tocompress magnetostrictive material 105 efficiently. In order totranslate the force from aerogel 125 to magnetostrictive material 105, aforce plate 135 is utilized.

Once the mechanical energy in aerogel 125 reaches magnetostrictivematerial 105, magnetostrictive material 105 is compressed via forceplate 135 at a certain frequency (e.g., approximately 100 times persecond), producing an oscillating magnetic field. The magnetic fieldcauses the state of the coil, which is wrapped around magnetostrictivematerial 105, to move to a varying magnetic flux environment. Becausethe coil is in a varying magnetic flux environment, an electrical field(e.g., a current) is induced in the coil to produce electrical power.

Located near magnetostrictive material 105 are Bellville washers 120.Bellville washers 120 are configured to prevent alternator 100 frombeing over-constrained, allowing force plate 135 to move.

It should be appreciated that alternator 100 does not require a pistonto be moving in order to produce electrical power as the parts inalternator 100 are compressing. Further, if a moving-part Stirlingengine is replaced with a non-moving-part Stirling engine, then agenerator having no moving parts can be achieved. It should also beappreciated that alternator 100 may be scalable, such that multiplealternators can be stacked upon each other. Alternator 100 may also varyin size depending on the frequency desired.

As shown in FIG. 1B, alternator 100 may also be used as a resonator. Insuch an embodiment, a large amplitude wave 145 that is received byaerogel 125 or steel rod (not shown), and is reduced to a loweramplitude wave (not shown). The lower amplitude wave has a high forcethat collides with force plate 135, causing magnetostrictive material105 to compress. The compression of magnetostrictive material 105 allowselectricity to be generated.

However, because not all of the compression is converted to electricity,the unconverted amount of compression is configured to bounce. This maycause magnetostrictive material 105 to re-expand, creating a lowamplitude wave (not shown). The low amplitude wave is configured totravel to aerogel 135 and is converted to a high amplitude wave 150.High amplitude wave 150 is then transmitted to the Stirling engine toprovide resonance.

Some embodiments of the present invention pertain to an oscillatingpressure wave that is converted into a low amplitude pressure wave tocompress the magnetostrictive material in order to generate electricalpower. As a result, bearings, lubrication, etc., are not required,lowering operational cost. The alternator described herein may also beused for generating power in vehicles (air, sea, land, or space), aswell as buildings. It should be appreciated that the alternatordescribed herein may produce electrical power, create a resonance forthe Stirling engine, provide control of the Stirling engine, and createun-amplified pressure wave in the Stirling engine that can be amplifiedat a later time.

It will be readily understood that the components of the invention, asgenerally described and illustrated in the figures herein, may bearranged and designed in a wide variety of different configurations.Thus, the detailed description of the embodiments is not intended tolimit the scope of the invention as claimed, but is merelyrepresentative of selected embodiments of the invention.

The features, structures, or characteristics of the invention describedthroughout this specification may be combined in any suitable manner inone or more embodiments. For example, the usage of “certainembodiments,” “some embodiments,” or other similar language, throughoutthis specification refers to the fact that a particular feature,structure, or characteristic described in connection with an embodimentmay be included in at least one embodiment of the invention. Thus,appearances of the phrases “in certain embodiments,” “in someembodiments,” “in other embodiments,” or other similar language,throughout this specification do not necessarily all refer to the sameembodiment or group of embodiments, and the described features,structures, or characteristics may be combined in any suitable manner inone or more embodiments.

One having ordinary skill in the art will readily understand that theinvention as discussed above may be practiced with steps in a differentorder, and/or with hardware elements in configurations that aredifferent than those which are disclosed. Therefore, although theinvention has been described based upon these preferred embodiments, itwould be apparent to those of skill in the art that certainmodifications, variations, and alternative constructions would beapparent, while remaining within the spirit and scope of the invention.In order to determine the metes and bounds of the invention, therefore,reference should be made to the appended claims.

The invention claimed is:
 1. An apparatus, comprising: an aerogelmaterial configured to continuously transition from a lower impedance toa higher impedance in one direction, and therefore opposite in theopposite direction, and configured to permit the transmission of anacoustic wave therethrough; and magnetostrictive material configured togenerate an oscillating magnetic field when the magnetostrictivematerial is compressed by the acoustic wave transmitted through theaerogel material.
 2. The apparatus of claim 1, wherein the aerogelmaterial is configured to receive the acoustic wave from a Stirlingengine.
 3. The apparatus of claim 1, further comprising: a force plateconfigured to translate force generated by the acoustic wave into themagnetostrictive material.
 4. The apparatus of claim 1, furthercomprising: a plurality of pre-stressed bolts configured to apply apredetermined amount of compression to the magnetostrictive material;and a plurality of pre-stress permanent magnets configured to generate amagnetic field to cause the magnetostrictive material to remain in acompressed state.
 5. The apparatus of claim 1, further comprising: acoil configured to produce electrical power when the magnetostrictivematerial generates the oscillating magnetic field.
 6. The apparatus ofclaim 5, wherein the coil is configured to surround the magnetostrictivematerial.
 7. The apparatus of claim 1, further comprising: a protectivediaphragm configured to prevent the aerogel from breaking; and animpedance layer support surrounding the aerogel, and configured tomaintain a position of the aerogel.
 8. An apparatus, comprising: a waveabsorbing impedance matching material configured to continuouslytransition from a lower impedance to a higher impedance in onedirection, and therefore opposite in the opposite direction, andconfigured to permit the transmission of an acoustic wave therethrough;and a compressing material configured to generate an oscillatingmagnetic field when the compressing material is compressed by theacoustic wave transmitted through the wave absorbing impedance matchingmaterial.
 9. The apparatus of claim 8, wherein the absorbing material isconfigured to absorb the acoustic wave from a Stirling engine to preventreflection.
 10. The apparatus of claim 8, further comprising: a forceplate configured to translate force generated by the acoustic wave intothe compressing material.
 11. The apparatus of claim 8, furthercomprising: a plurality of pre-stressed bolts configured to apply apredetermined amount of compression to the compressing material; and aplurality of pre-stress permanent magnets configured to generate amagnetic field to cause the compressing material to remain in acompressed state.
 12. The apparatus of claim 8, further comprising: acoil configured to produce electrical power when the compressingmaterial generates the oscillating magnetic field.
 13. The apparatus ofclaim 12, wherein the coil is configured to surround the compressingmaterial.
 14. The apparatus of claim 8, further comprising: a protectivediaphragm configured to prevent the absorbing material from breaking;and an impedance layer support surrounding the absorbing material, andconfigured to maintain a position of the absorbing material.
 15. Theapparatus of claim 8, wherein the absorbing material comprises aerogelor a steel bar.